function J = J_SA_p( m, param)

    % Calculates J\prime(m) under offer matching
     
    J = (1-param.omega_1)./rho_fun(1,'R',param)  ...
            + param.J_1*m.^(param.gamma_N_1).*param.gamma_N_1./m + param.J_2*m.^(param.gamma_N_2).*param.gamma_N_2./m;

end